1. Field of the Invention
The invention relates to a prefabricated modular helical earthquake and fire escape structure for attachment to or incorporation in a multiple story building.
2. Description of the Prior Art
High rise buildings at the present time utilize conventional stairwells for evacuating occupants of the building in the event of an earthquake or fire. It has been found that fires often spread from one floor to another through these stairwells, which are usually the only route to safety for the occupants of the building, particularly if the elevators are inoperative. This spreading of the fire occurs because the stairwells comprise uninterrupted vertical shafts which create an upward draft enhanced by heated air which moves rapidly upward, spreading the fire. Flames and smoke in the stairwells prohibit their use for escape purposes and make it practically impossible for occupants of the building to pass the level where the fire originated.
While helical slides have been proposed for use as emergency escapes, as shown in prior patents such as U.S. Pat. Nos. 277,156, 826,613, 935,142 and 1,194,098, such shapes have apparently been considered too intricate and complex to be built in the conventional way and the labor costs prohibitively high to make them practical and economically feasible for use in modern high rise buildings.